Rotary air compressor



United States Patent Inventor Henri Chapuis 26, rue des Renaudes, Paris, France Appl. No.- 834,031

Filed June 17, 1969 Patented Nov. 24, 1970 Priority July 17, 1968 France No. 159,493

ROTARY AIR COMPRESSOR 8 Claims, 1 Drawing Fig.

US. Cl 418/84, 184/6 Int. Cl F04c 29/02, F01 m 1/00 Field of Search 230/207,

[56] References Cited UNITED STATES PATENTS 2,701,684 2/1955 Hirsch 230/207 2,867,376 1/1959 Keir et al. 230/207 Primary Examiner-Robert M. Walker Attorney-Spencer 8L Kaye ABSTRACT: A rotary air compressor having a rotor and a stator, a suction pipe connected to the stator and connected to atmosphere by a valve controlled by a pilot circuit, a delivery pipe connected to a reservoir, and an admission pipe connected between the suction and delivery pipes, the delivery pipe being connected to atmosphere by a normally closed valve controlled by the pilot circuit and the admission pipe being connected to an auxiliary lubricant reservoir and to a pressurised principal lubricating circuit.

Patented Nov. 24, 1970 Sheet I of 2 INVENTOR.

HARRY cf 6T4DLEZ 6pm,, 27W

Patented Nov. 24,1970 5 32,542,497.

Sheet & of 2 I lnvenlor Henrl cvupuws Qlowwc 711% A Horn e y ROTARY-AIR COMPRESSOR BACKGROUND or THE INVENTION chambers during the no-load operation of the compressor,

which causes an unnecessary power consumption.

A second type of circuit is subject to the pressure prevailing in the delivery reservoir. During no-load operation of the compressor, the lubricatingand cooling liquid is delivered under the pressure prevailing in the reservoir. Thus one is caused to maintain a significant residual pressure in the moving chambers of the compressor, which partially balances that prevailing in the reservoir, the compressor obviously not having to deliver compressed air into the latter. By virtue of this arrangement the lubricating liquid penetrates into the moving chambers in limited quantity, which removes all danger of fracture of the rotating assembly. Nevertheless, as above, the compressor during its-no-load operation consumes a relatively large power, even though this is unnecessary to maintain the counter pressure.

SUMMARY OF THE INVENTION The present invention has principally for object to reduce the power absorbed by a rotary compressor during its no-load operation, irrespective of the lubricating cooling circuit utilised.

It also has for object to reduce the quantity of liquid circulating during no-load operation, adapting it automatically to the lubrication requirements.

In order to achieve the above-mentioned objects, the present invention proposes improving known rotary compressors of the type comprising, about a rotor, a stator having on the one hand a suction pipe connected to atmosphere through the intermediary of a valve controlled by a pilot circuit the pilot element of which is subject to the pressure prevailing in the compressed air reservoir, on the other hand a delivery pipe connected to this reservoir, finally between these two pipes and in the compression trajectory of the rotor, an admission pipe connected to the pressurised lubrication andcooling circuit. Preferably but nonrestrictively these rotary compressors are ofthe vane type and their lubrication and cooling circuit is controlled by the compressed air ofthe reservoir.

In accordance with the invention, in the improved rotary compressor, the delivery pipe is also connected to atmosphere through the intermediary offa normally closed valve the opening of which is controlled by the aforementioned pilot circuit and the admission pipe is connected on the one hand directly to an auxiliary lubricant reservoir and on the other hand, through a pilot-controlled isolating element, to the pressurised principal lubricating circuit.

The improvement defined above utilises a process consisting in closing the air suction and connecting the delivery to atmosphere in order to cause a depression in the moving chambers of the compressor and to substitute for the normal lubricating and cooling circuit a low-delivery auxiliary circuit controlled by the aforementioned depression.

Thus as soon as the reservoir is at its maximum pressure the compressor rotates under no load and expels the air which it contains to atmosphere. Very rapidly no further compression is produced and the result is an important gain over the power absorbed by the compressor during its no-load operation. Furthermore and at the same time, the principal circuit ceases to deliver lubricant into the compressor and it is the auxiliary circuit which takes over under'the influence of the vacuum which has appeared in the compressor.

Another particularly important advantage consists in the simplicity of design and realisation of this improved compressor, i n its great operational security, in its reliability and in its low cost price.

According to a particularly advantageous form of embodiment, the air circuit comprising the valve for connecting the delivery pipe to atmosphere is connected to the said atmosphere through the intermediary of an expansion chamber the lower lubricant-recovery part of which is connected through a limited passage to the suction pipe of the compressor. The suction pipe of the compressor is connected to atmosphere through the intermediary of a limited passage controlling the no-load rate, this passage preferably being limited by a calibrated valve mounted in the circuit connecting the said expansion chamber to the said pipe. The auxiliary lubricant reservoir is disposed beneath a reduced orifice formed in the conduit conducting the compressed air and the lubricant issuing from the delivery pipe, to the compressed air reservoir and the principal lubrication and cooling circuit, this orifice being provided in an impact separation zone and preferably in a sharp bend in the said conduit. The aforementioned insulating element of the principal lubricating and cooling circuit is a normally open valve the closure of which is controlled by the 'pilot circuit.

Various other characteristics of the invention will also appear from the following detailed description.

BRIEF DESCRIPTION OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENT In order to facilitate understanding of the following, a vane type compressor has been selected the lubricating and cooling circuit ofwhich is controlled by the compressed air. As is well known, this compressor'comprises a rotor l equipped with vanes 2 and mounted in a stator 33, this rotor rotating in the direction ofthe arrow F.

The stator is equipped with a suction pipe 4 situated in the zone where the capacity of the moving chambers of the rotor is greatest. The pipe 4 is connected to atmosphere through the intermediary ofa pilot valve 5, a non return valve 6 and a filter 7. The valve Sis normally open and its closure control element can be of any known type whatever: pneumatic, hydraulic, electromagnetic or other. In the example as represented it is of the pneumatic type and therefore it is connected to a conduit 8 connected to a pilot element 9. The nonreturn valve 6 is normally closed and opens under the suction effect created in the chamber 10 by the compressor. The stator 3 also possesses a delivery pipe 11 situated in the zone where the capacity of the moving chambers of the rotor I is smallest. This pipe it is connected by a conduit 12 and through a nonreturn valve 13 to a reservoir 14. Moreover the utilisation circuit or circuits is or are connected to this reservoir. The nonreturn valve 13 is normally closed and opens when the pressure delivered by the compressor is greater than that existing in the reservoir.

The reservoir 14 is intended to contain in its lower part the lubricating and cooling liquid hereinafter called lubricant. This lubricant is thus always subject to the pressure of the compressed air contained in the reservoir and can thus be delivered under this pressure. It is conducted by a conduit 15 through a cooling apparatus 16 and a filter 17 to an admission chamber 18 opening through an orifice 19' into the stator 3. The orifice I9 is situated between the pipes 4 and ll in the zone where the capacity of the moving chambers of the rotor l is diminishing. The pilot element 9 to which the conduit 8 for control of the valve 5 is'connected is branched on the reser voir 14 at its upper part. This pilot element, known per se, is subject to the pressure prevailing in the reservoir and when the said pressure reaches a preregulable tripping threshold it places the conduit 8 in communication with the reservoir. The valve 5 is then placed under pressure, which causes its closure so that the compressor cannot suck atmospheric air. When the pressure in the reservoir 14 drops by reason of the utilisation of the compressed air and reaches a different retripping threshold, the pilot element 9 connects the conduit 8 to atmosphere, isolating the reservoir, and the result is that the valve opens.

in normal operation, the valve 5 being open, the compressor sucks atmospheric air through the pipe 4, compresses it and delivers it through the pipe 11 and the conduit 12 into the reservoir 14 until the pressure in the latter reaches the aforementioned tripping level. At the same time the compressed air forces the lubricant contained in the reservoir 14 towards the chamber 18. On passage through the apparatus 16 the lubricant is cooled and in passing through the filter 17 it deposits the impurities which it contains. The lubricant contained in the chamber 18 gushes under pressure and with great delivery into the stator through the orifice 19. The delivery is such that the lubricant fills only a very small part of the moving chambers of the rotor but nevertheless ensures effective lubrication and sufficient withdrawal of the calories due to the heating of the compressor. The lubricant thus introduced into the compressor is evacuated at the same time as the compressed air through the pipe]! and the conduit 12 towards the reservoir 14.

According to the invention a conduit 20 is connected in parallel between the conduit 12 and an expansion chamber 28 surrounding the suction chamber 10. A pilot valve 21 is mounted in series in this conduit. Thus its control element is connected to a-conduit 22 branched from the pilot conduit 8. The valve 21 is normally closed and it opens under the control of its pilot circuit when the pressure in the reservoir 14 reaches the tripping threshold. The branch conduit 20 terminates in the annular chamber 28 which opens into the suction chamber between the filter 7 and the valve 6 through a passage of reduced section (hole, slot or other) situated above the bottom of the said chamber 28, A small calibrated valve 30 is connected to this chamber below the passage 29 and connected through a pipe 31 to the suction pipe 4. Moreover the valve 6, which is normally open, is provided only to prevent escape of air and lubricant at the moment of stopping of the compressor.

Furthermore a second lubricating circuit is provided to substitute for the principal circuit to 19 when the compressor is rotating under no load. This second circuit comprises a reservoir 23 connected to the conduit 12 at a region where the lubricant issuing from the compressor can escape. In the example as represented the reservoir 23 is situated beneath the compressor and communicates through a relatively narrow orifice 24 with the conduit 12. The orifice 24 is formed in an elbow of this conduit so that the lubricant carried by the compressed air comes and strikes upon the said elbow and can escape through the said orifice towards the auxiliary storage reservoir 23.

The reservoir 23 communicates with the suction chamber 18 through a conduit 25 on which a calibrated, fixed or regulable choke 25a is provided intended to regulate the delivery of oil during no-load operation. Moreover the communication of the admission chamber 18 with the conduit 15 is controlled by a pilot valve 26. This is' normally open and must be closed when the compressor is operating under no load. To this end the control element of the valve 26 is connected to a conduit 27 branched on the pilot conduit 8. Under these circumstances as soon as the pressure in the reservoir 14 reaches the tripping level, the pilot element 9 connects the conduit 8 to the said reservoir and causes closure of the valve 26 at the same time as the closure of the valve 5 and the opening of the valve 21.

The improved compressor according to the invention thus operates in the following manner: in operation under load, the pilot element 9 connects the conduit 8 and the branch conduits 22 and 27 to atmosphere. The valves 5 and 26 are then open and the result is that the atmospheric air can penetrate into the compressor, that this air is compressed and conducted towards the reservoir 14 and that the principal lubricating circuit 15 to 19 delivers the lubricant to the compressor at high pressure and with great delivery. The auxiliary reservoir 23 fills automatically with lubricant which will be available at the 5 time of no-load operation. At the same time the valve 21 is closed and consequently interrupts all communication between the delivery pipe of the compressor and atmosphere.

As soon as the pressure in the reservoir 14 reaches the tripping level, the pilot element 9 establishes this pressure in the conduit 8 and in theconduits22 and 27. The result is that the valve 26 closes and cuts off the lubricant supply of the compressor through the principal circuit 15 to 17. At the same time the valve 5 closes while the valve 21 opens. Thus the compressor can no longer admit atmospheric air. It rotates under no load and expels the air which it contains towards the chamber 28 through the conduit 20. the compressed air of the reservoir 14 being unable to return towards the compressor since the nonreturn valve 13 is closed. Thus a partial vacuum establishes itself in the moving chambers of the compressor and in the admissionchamber 18, so that the power consumed by the compressor rotating under no load is considerably reduced. Moreover the depression which has appeared in the admission chamber 18 and the moving chambers of the compressor has the effect ofsucking the lubricant contained in the reservoir 23 and distributing it to the compressor at reduced rate, just sufficient to ensure lubrication. The return ofthis oil and the regulation of the vacuum are ensured by the small valve 30 interposed between the expansion chamber 28 and the suction chamber 4. Thus this oil returns to the auxiliary reservoir 23 in order to carry out the auxiliary lubricating cycle.

As soon as the pressure in the reservoir 14 drops and reaches the retripping threshold, the pilot element 9 connects the conduit 8 and the inlet conduits 22 and 27 to atmosphere. The valve 21 closes and the valves 5 and 6 open. The compressor can then operate under load as described above. Moreover the invention is applicable to the case where the compressor comprises a lubricating and cooling circuit placed under pressure by a pump driven for example by the same element as the compressor. In this case the pilot valve 26 is replaced by another which is of the two-way type. This valve has the effect of connecting, through one of its ways the pressurised lubricant conduit 15 to the admission chamber 18, when the compressor is operating under load, that is to say when the pilot conduit 27 is connected to atmosphere. This valve also permits, when the compressor is operating under no load and the pilot conduit 27 is under pressure, of connecting the conduit 15 to the admission ofthe pump.

Finally the pilot circuits and the pilot valves can be ofa type other than pneumatic. It is simply sufficient that the pilot element 9 be sensitive to the pressure prevailing in the reservoir 14. For example the valves can be of the electromagnetic or electromechanical type and their respective control elements are then connected to a current source through the intermediary of relays themselves controlled by a pilot element of the piezo-electric type.

The invention is not limited to the form of embodiment as represented and described in detail, since various modifications can be effected therein without departing from the scope of the invention.

1 claim:

1. In a rotary compressor, preferably of the vane type having a lubricating and cooling circuit which is controlled by the compressed gaseous fluid, comprising a compressed air reservoir, a rotor, a stator about the rotor, a suction pipe, a valve, said suction pipe being connected to said stator and to atmosphere through the intermediary of said valve, a pilot circuit controlling said valve, a pilot element in the pilot circuit, which element is subject to the pressure prevailing in the compressed air reservoir, a delivery pipe connected to the reservoir, a lubricant admission pipe between these two pipes and on the trajectory of compression of the rotor, and a pressurised lubricating and cooling circuit connected to the lubricant admission pipe, the provision of a normally closed valve connecting the delivery pipe to atmosphere, the opening of which valve is controlled by the aforementioned pilot circuit, an auxiliary lubricant reservoir to which the admission pipe is connected, and a pilot-controlled isolating element connecting the admission pipe to the principal pressurised lubricating and cooling circuit.

2. Rotary compressor according to claim 1, further comprising an expansion chamber and a limited passage, wherein the air circuit comprising the valve connecting the delivery pipe to atmosphere is connected to said atmosphere through the intermediary of said expansion chamber the lower, lubricantrecovery part of which is connected through said limited passage to the suction pipe of the compressor.

3. Rotary compressor according to claim 1, further comprising a limited passage and a calibrated valve, wherein the suction pipe of the compressor is connected to atmosphere through the intermediary of said limited passage controlling the no-load rate, this passage being preferably defined by said calibrated valve mounted on the circuit connecting the said expansion chamber to the said pipe.

4. Rotary compressor according to claim 1, further comprising a reduced orifice and an impact separation zone, wherein the auxiliary lubricant reservoir is disposed beneath said reduced orifice formed in the conduit conducting the compressed air and the lubricant issuing from the delivery pipe towards the compressed air reservoir and the principal lubricating and cooling circuit, this orifice being provided in said impact separation zone preferably in a sharp bend of the said conduit.

5. Rotary compressor according to claim 1, further comprising a calibrated, preferably regulable orifice establishing communication between the auxiliary lubricant reservoir and the admission pipe.

6. Rotary compressor according to claim 1, in which, in the case where the principal lubricating and cooling circuit is placed under pressure by the compressed air of the reservoir, the aforementioned element for isolating this circuit is 21 normally open valve the closure of which is controlled by the pilot circuit.

7. Rotary compressor according to claim 1, in which, in the case where the principal lubricating and cooling circuit is placed under pressure by a pump, the aforementioned isolating element is a two-way valve normally connecting this circuit to the admission pipe of the compressor and controlled by the pilot circuit to close the said circuit on its pump.

8. Rotary compressor according "to claim 1, in which the pilot circuit is of the pneumatic type and the control elements are pilot valves. 

